How to create a new tileset using OpenRA TilesetBuilder

This one is a user-friendly GUI tool that is however not shipped in any releases so you need to compile yourself. You also need to edit defaults.yaml in the OpenRA.Tilesetbuilder folder if you don't want to edit Dune 2000 tilesets. Once done start OpenRA.TilesetBuilder.exe It will ask you for a palette (or extract it from the file itself) and a tile size. RA and CnC use 24 (default) while D2k uses 32. You can select tiles by keeping the mouse pressed and assign terrain types using the buttons on the left. Toggle the overlay in the main toolbar to see which is already marked. Click save to save a *.tsx XML file next to your .png file and export to find them in your My Documents\OpenRA\Tilesets folder together with the .yaml file required for OpenRA.